Carrier sense multiple access with collision resolution

Carrier sense multiple access with collision resolution

Carrier sense multiple acc ess with collision resolutio n IEEE communications letters Hyun-Ho Choi, Jung-Min Moon, In-Ho Lee, and Howon Lee

CSMA/CD A transmitting station can detect a c ollision while transmitting However, the CSMA/CD protocol is on ly possible in a wired network A wireless network has deafness prob

lem (the receiver of the transmitting station is overwhelmed by its own tra nsmission power) Wireless CSMA/CD (WCSMA/CD)

Each station allocates a short CD slot randomly within a fixed CD period Senses the channel at the selected CD slot to determine whether a collision occurs or not CSMA/CR

It extends the WCSMA/CD protocol CSMA/CR protocol identifies a collisio n by additional sensing after data tra nsmission starts One station that first detects a collisi on transmits a jam signal

CSMA/CR No collision occurs CSMA/CR A collision is detected

Cases of a collision is not detected i n CSMA/CR Case 1 Cases of a collision is not detected i

n CSMA/CR Case 2 Implementation issue 802.11 standard defines a slot time (aSlotTime) as a basic time unit requi

red for the channel sensing and acce ssing For the CSMA/CR, a CD slot time (aC DSlotTime) should satisfy Throughput analysis

From theh Bianchis CSMA/CA analysi s, - the probability that in a slot time there is at least one transmission - the probability that a transmission is succ essful

- the probability that a transmission is colli ded Throughput analysis The collision probability of - WCSMA/CD

- CSMA/CR Throughput analysis The collision detection probability of WCSMA/CD

The collision resolution probability of CSMA/CR Normalized throughput

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